Dual armature motor/generator with flux linkage between dual armatures and a superconducting field coil

ABSTRACT

The present invention relates to cylindrical rotating electric machines which comprise armature and field coils, with either the field coil or the dual armature being the rotating component. The dual armature is composed of two concentric cylindrical sets of coils with the field coil situated in the gap between the inner and outer armature sections. Relative rotational motion between the field and armature coils can be achieved by having either one be the rotor. By using two armature coil sections, one inside the field coil aperture and the other external to the field coil, the flux linkage between the armature and superconducting field coil can be approximately doubled. This is a more efficient use of the superconductor. The increased flux linkage in the invented technology produces a substantially higher power density than can be obtained with current conventional superconducting machine technology.

RELATED APPLICATION DATA

This application is related to Provisional Patent Application Ser. No.61/168,025 filed by Carl Leonard Goodzeit on Apr. 9, 2009 entitled“Split Rotor Motor/Generator,” and priority is claimed for this earlierfiling under 35 U.S.C. §119(e). The Provisional Patent Application isalso incorporated by reference into this utility patent application.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a dual armature electric motor or generatorwith flux linkage between the dual armatures and a superconducting fieldcoil for applications in propulsion motors for marine, air, and landvehicles, or for electric power generation in wind power andhydroelectric generating stations.

BACKGROUND OF THE INVENTION

A cylindrical, rotating electrical machine consists of a field coil thatproduces a magnetic field and an armature. The armature consists of aseries of current loops in the form of a coil that links the magneticflux produced by the field coil. Relative rotational motion between thearmature and the field coil then produces a generated voltage in thearmature due to the rate of change of flux linkage in the armaturecoils. The power of the machine is proportional to the square of thegenerated voltage that is produced in the armature. Rotating machinesare usually AC (synchronous) or DC types.

For example, in a “synchronous machine” such as a conventional ACgenerator, a rotating field coil is situated within the aperture of astationary armature, which may contain multi-phased coils. The rotatingfield interacts with the stationary armature to produce asinusoidal-varying voltage in the armature coils.

Another example of a rotating machine is a conventional DC-type machinein which a rotating armature is located in the aperture of a stationaryfield coil. The armature coils in this case also experience a generatedalternating voltage, but the armature current is rectified bycommutation or by external rectification to produce a voltage that issubstantially DC.

It is seen that the synchronous machine derives its armature fluxlinkage from the field external to the field coil, while the “DC type”machine derives its armature flux linkage from the field inside theaperture of the field coil. This amounts to “wasted flux” in both casesbecause the field on the inside of the field coil of the synchronousmachine is not linked to the coils of the armature and the field on theoutside of the field coil in the “DC type” machine is not linked to thecoils of the armature.

In the case of DC machines, there are two configurations that have beenused that include a superconducting field coil with anon-superconducting armature or rotor. One is the homopolar machine witha superconducting field coil and a high-current resistive rotor thatconnects to an external circuit. In this case there is only oneeffective current path in the rotor and thus the machine can onlyproduce power at low voltage and high current. However, the current is aconstant voltage DC. The second type of DC machine can be considered asa rectified AC machine that uses, for example, a three-phase winding forthe armature coils, coupled with a full-wave three-phase rectifier.

A known example of the homopolar motor is described by Michael J.Superczynski, Jr., and Donald J. Waltman in IEEE Transactions on AppliedSuperconductivity, Vol. 7, No. 2, June 1997, “Homopolar Motor with HighTemperature Superconductor Field Windings”. The machine described inSperczynski uses a rotor that is supplied by 30,000 A of current inorder to produce the desired power. This high current is necessarybecause the rotor provides only a single current path through themagnetic field, and the output power is proportional to the totalcurrent, the field strength, and the length of the current path in therotor. Thus, the output of the machine of a fixed size and magneticfield can only be increased by increasing the current passing throughthe rotor.

An externally excited DC machine, using the principle of rectified ACwith a superconducting field coil and a normal-conducting armature isdisclosed in U.S. Pat. No. 5,032,748, Jul. 16, 1991, to Sakuraba et al.

Lewis and LeFlem describe a superconducting electrical machine of thesynchronous type in patent application document US 2008/0161189A1, whichwas published Jul. 3, 2008. The device described in Lewis is asynchronous electrical machine with a rotating field coil that comprisestwo concentric cylindrical coils and a stationary single armature coilthat is situated in the gap between the two field coils. This splitfield coil configuration allows the armature to link the same amount offlux that can be linked from an un-dual field coil that must operatewith a higher field than either of the dual field coils. In this case,the operating margin of the field coils is increased because they cannow run at a lower current that does not exceed the critical currentdensity in the superconductor. This approach is designed to allow morechoices for superconductor, but this configuration does notsignificantly change the power density of the machine since the armaturedoes not link with all of the field flux.

Caroon describes a prior art configuration in U.S. Pat. No. 7,400,077.This Caroon machine has a central rotatable axle, a first ‘fieldarmature’ disposed around and attached to the axle, a second ‘fieldarmature’ that is disposed around the first field armature and alsoattached to the axle, and a stationary ‘electromagnetic member’ that isdisposed between the first and second field armatures and is attached tothe machine housing. The ‘field armatures’ each contain a plurality offield magnets while the electromagnetic member includes a plurality ofelectromagnets. The arrangements of field magnets and electromagnets onthe rotors and stator are much more complex than those described in thepresent invention.

Minagawa describes a prior art configuration in U.S. Pat. No. 6,710,492.This Minagawa machine claims a stator with a plurality of coils that aresupplied with a polyphase AC current to cause two rotors with differentarrangements of magnets and coils to move independently of each other.In the claims, the two rotors are coaxial and concentric in someconfigurations and undefined in other claims. The position of the statoris also not defined in any of these claims. The description of themachine in the text shows a triple layer structure with the statorpositioned between these two rotor coils but in the final paragraphs itis stated that “it is possible to apply the invention to amotor/generator disposing two rotors coaxially.” The arrangements ofmagnets and coils on the rotors and stator are much more complex thanthose described in the present invention.

Smith describes a prior art configuration in U.S. Pat. No. 3,742,265This machine claims various arrangements of three concentric and coaxialcylindrical elements, of which one is a superconducting field windingand the other two are normal conducting armatures. Some of the claimsdescribe placement of the field winding in the center between the twoarmature windings, however, the stated objective in claim 1 is not thesame as the present invention, which operates differently to produce adifferent functional result. The present invention can also use allsuperconducting elements or field coils, and the present invention canalso use normal conductors in armatures.

SUMMARY OF THE INVENTION

This invention relates to cylindrical rotating electric machines whichcomprise armature and field coils, with either the field coil or thedual armature being the rotating component. The dual armature iscomposed of two concentric cylindrical sets of coils with the field coilsituated in the gap between the inner and outer armature sections. Thesingle field coil is placed in a radial gap between two concentriccylindrical armature coils.

Relative rotational motion between the field and armature coils can beachieved by having either one be the rotor; the preferred configurationwould be for the armature coils to be the rotor. By using two armaturecoil sections, one inside the field coil aperture and the other externalto the field coil, the flux linkage between the armature andsuperconducting field coil can be approximately doubled. This is a moreefficient use of the superconductor. The increased flux linkage in theinvented technology produces a substantially higher voltage than can beobtained with current conventional superconducting machine technology.

This arrangement links flux from the field coil to the armature sectionsin both the inner and outer regions of the field coil. Thus, a machineof this configuration can effectively double the amount of flux linkedbetween the field and the armature as a conventional machine of the samesize that links flux on only one side of the field coil.

The dual armature is generally the rotating member of the machine andcan be comprised of superconducting coils, resistive coils operating atcryogenic temperature, or resistive coils operating near ambienttemperature. The field coil is generally a stationary superconductingcoil and operates at a steady state excitation current to produce astrong magnetic field in its aperture and external to the coil. Althoughthe flux density in the aperture is higher than that outside the fieldcoil, the total amount of flux in both spaces is the same, and thistotal flux can be linked by the coils of the inner and outer sections ofthe dual armature.

A specific embodiment of the present invention discloses superconductingelectric machines that use a plurality of multi-turn coils in anarmature located in an externally excited magnetic field. The armatureis a dual configuration of two concentric cylindrical sections with thefield coil placed between them.

The superconducting field coil is mounted in a cryogenic containmentvessel. If the armature coils are to be at a higher temperature, thiscryogenic vessel will be sized to fit in the space between the twosections of the dual armature. This cryogenic containment vessel withthe field coil is called the cold mass and is supplied with a cryogen toallow operation at superconducting temperatures. The cold mass ismounted in a vacuum vessel whose outer walls may comprise the frame ofthe machine. The reaction torque of the stationary field coil istransmitted to the frame of the machine by means of a low heat leak,high torque support system.

The armature coils may be enclosed within their own cryogenic vessel sothat they can be cooled by a separate cryogenic supply/exhaust systemthat permits them to operate at a temperature different than that of thefield coil. The armature rotor is supported from the exterior frame ofthe machine by means of support members with bearings to allow it torotate freely.

A primary objective is to provide improved electric machines by using asuperconducting field coil (stator coil) in conjunction with a dualarmature that can provide almost twice the flux linkage between thearmature and the field coil. The invented technology provides asubstantially increased power density from the same size machine thatuses conventional configurations.

A secondary objective is to provide improved electric motors for use inmarine, air, and land vehicle propulsion by using a superconductingmachine that can provide a large amount of power at high voltage even atvery low operating speed.

A third objective is to provide improved electric power generators forwind or hydroelectric power sources by using a superconducting machinethat can provide a large amount of power at high voltage even at verylow operating speed.

A fourth objective is to provide improved electric machines that usesuperconducting coils in both the stator and rotor, thus increasing thepower density, reducing the mass of the machine, and increasing theoverall electrical efficiency.

A fifth objective is to provide a fully superconducting electric machine(i.e. superconducting field and rotor coils) that is especially suitablefor the use of high temperature superconducting (HTS) materials. Thisfully-superconducting machine achieves a very high power to mass ratioand can operate at the higher range of cryogenic temperatures forsuperconducting materials. These HTS materials are inherently brittle innature and suffer degradation of superconducting properties whenspecified strain limits are exceeded. The geometry of the double-helixsuperconducting multi-turn coils that can be used in this invention isespecially suitable for the application of high temperaturesuperconductors since the coils can be easily designed so that the coilwinding process will accommodate the allowable minimum bend radius thatwill prevent degradation of the superconductor.

A sixth objective is to provide an electric machine with asuperconducting field coil with a low enough heat leak (i.e. gain fromexternal sources) so that it can benefit from the use of low temperaturesuperconducting materials such as NbTi. This is accomplished byproviding a high torque, low heat leak support system to handle thereaction torque on the field coil.

One end of the armature assembly is generally provided with a hightorque capacity coupling to transmit mechanical power to or from anexternal device by means of a high torque capacity, low heat leak shaftassembly. The opposite end of the rotor is provided with a low heat leakextension tube that extends through the vacuum tank to ambienttemperature. Electrical connections are provided between the armaturecoils and the slip rings and brushes mounted on the ambient temperatureregion of the extension tube. The extension tube can also containprovisions for supplying and exhausting cryogenic fluid from the rotorcontaining the armature coils.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention will become more readilyunderstood from the following detailed description and appended claimswhen read in conjunction with the accompanying drawings in which likenumerals represent like elements and in which:

FIG. 1 is a cross-sectional diagram that shows the magnetic fieldproduced by the field coil and the flux linkage with the inner and outersections of the dual armature;

FIG. 2 is a view of the coil geometry in a double-helix dipole;

FIG. 3 shows principle design features of an embodiment of theinvention; and,

FIG. 4 shows coil geometry in a race-track dipole configuration for anembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of this invention is a 2-pole machine thatcontains a rotating armature with three 2-pole coils in each of the twoconcentric rotor sections, that are placed in an external multi-polefield of order N=2 created by a stationary superconducting field coil.The three armature coils of each rotor section are oriented such thatthe spatial angles of their magnetic axes are 120° apart and therespective coils in each armature section are connected in series so thegenerated voltages in the coils of the two sections are added. Otherembodiments of this machine can be made with four and more poleconfigurations for both the rotor and field coils.

As set forth in the present invention, the armature of a machineconsists of two separate sets of coils, one set placed in the apertureof the field coil to link flux inside the field coil and the other setplaced outside the field coil to link with the flux external to thefield coil, which results in approximately doubling the flux linkagebetween the armature coils and the field coil, thus approximatelydoubling the generated voltage. Furthermore, if the generated voltage isdoubled, the power of the machine is increased by a factor of four withthe same load resistance.

The greatest amount of magnetic flux for a modest size and weight deviceis achieved by using a superconductor for the field coil. It is notpractical to use a field coil with an iron core and resistive materialfor its windings because the magnetic field that can be achieved is notsufficient to produce a high power output. The armature coils could bemade with either superconductor or normal conductor materials, dependingon the requirements for the electrical device.

The dual armature machine disclosed in this document uses a completelydifferent principle than that of Lewis and LeFlem machine configuration.For example, the single field coil in the present invention is placed ina radial gap between two concentric cylindrical armature coils. Relativerotational motion between the field and armature coils in the presentinvention can be achieved by having either one be the rotor, while apreferred configuration would be for the armature coils to be the rotor.

By using two armature coil sections, one inside the field coil apertureand the other external to the field coil, the flux linkage between thearmature and superconducting field coil can be approximately doubled.This is a more efficient use of the superconductor. The increased fluxlinkage in the invented technology produces a substantially highervoltage than can be obtained with current conventional superconductingmachine technology. It should be noted that if the generated voltage ofan electrical machine is doubled, then the power of the machine isincreased by a factor of four using the same external load resistance.This configuration yields a substantial power density improvement for anelectrical machine. This dual armature configuration enables a machinethat can produce high voltage even at low rotor speeds, and is verydesirable for applications such as a wind turbine generator orpropulsion motor.

This invention discloses superconducting electric machines that use aplurality of multi-turn coils in the armature in an externally excitedfield. The armature is a dual configuration of two concentriccylindrical sections with the field coil placed between them. For thedevice disclosed in this patent, it is most suitable to use field andarmature coils of the “double-helix” configuration shown in FIG. 2.However, other cylindrical coil configurations, such as the race trackwinding shown in FIG. 4, could be used.

With reference to FIG. 1, the advantage of this dual-armature techniquecan be illustrated by using a two pole machine, whose coil cross-sectionis shown in FIG. 1. The dual armature consists of an inner section (103)and an outer section (101), each consisting of multi-turn coils. A fieldcoil (102) is situated between the two armature coil sections. The fieldcoil (102) generates the magnetic field indicated by the directionalarrows (104, 105). Thus, the inner section (103) of the armature linkswith the flux (104) inside the aperture of the field coil while theouter section (101) links with the flux (105) on the outside of thefield coil. With the inner and outer sections of the armature coilsconnected in series, almost twice the voltage can be generated in thearmature coils than with a conventional machine that links flux from acomparable field coil with only one armature coil section.

The field calculation for the dual armature shown in FIG. 1 uses a6-layer Double-Helix Dipole (DHD) field coil in the region between theinner and outer sections of the armature. The geometry of DHD coils isdescribed in FIG. 2. The dual armature uses three 4-layer DHD coils ineach of the armature sections. The armature coil poles are 120° apart inboth the inner and outer sections of the armature, for a three-phaseconfiguration. This dual armature effectively doubles the number ofturns that would be used in either the synchronous or DC type machine.The two coil sections of the dual armature, when connected in series,produce almost twice the voltage of one of the sections alone. Space isprovided between the field coil and the armature coil sections to allowfor structural reinforcement of the coils and thermal insulation of thesuperconducting field coil.

The calculations show that the field intensity (104) inside the apertureof the field coil is uniformly high while the field intensity (105) onthe outside of the coil is lower and decreases with the radial distance.Consequently the coil turns of the inner armature section are exposed toa higher field than those of the outer armature section. The linked fluxper coil equals the area of the coil times the field intensity, and theinner armature coils have a smaller radius and thus less surface areathan the outer armature coils. However, if the inner and outer coilshave the same total length, the inner coils could have more turns ofsuperconductor than the outer coils, as discussed in FIG. 2. The resultis that the inner and outer armature sections can be designed so thatthey each link almost the same amount of flux.

With respect to FIG. 2, the present invention is described that includesthe use of “double-helix coils” for the field excitation and armaturecoils. The double-helix dipole (DHD) coils are composed of multi-layerpairs of cylindrical coils that are wound as tilted loops that make anangle with the coil axis. The tilt angles of the 2 coils in a pair areopposite so that the axial components of the magnetic field cancel andthe resultant is a transverse magnetic field, perpendicular to the coilaxis. The use of DHD coils in this disclosed device facilitates thecomputation of the estimated performance of the machine. Mostimportantly, this configuration provides a lower cost and more easilymanufactured super conducting device than can be obtained usingconventional coils wound in a race track configuration.

The geometry of the double-helix superconducting multi-turn coils thatcan be used in this disclosed invention is especially suitable for theapplication of high temperature superconductors. These materials areinherently brittle in nature and suffer degradation of superconductingproperties when specified strain limits are exceeded. However, thedouble-helix coils can be easily designed so that the coil windingprocess will accommodate the allowable minimum bend radius that willprevent degradation of the superconductor.

The double-helix dipole (DHD) coils are composed of multi-layer coils ofthe type shown in FIG. 2. FIG. 2 shows the coil turns as tilted loops(201) that make an angle, α (202), with the coil axis (203). The turnshave an axial spacing, h (204). The end section of each coil layer hasan overhang length, L (205), that is equal to 2 times the coil radius, R(206), divided by tan α. Thus, if there are n coil loops, the totallength of the coil layer is equal to the overhang L (206) plus theproduct (207) of n times h.

In the preferred embodiment of this machine, the number of turns in thesmaller radii inner coils of the armature is increased in order to makethe total length of each coil the same as the length of the longest coil(the outer-most armature coil). In this way the flux linkage and thusthe generated voltage can be optimized for this embodiment of themachine.

The use of DHD coils in this example facilitates the computation of theestimated performance of the machine and, most importantly, provides alower cost and more easily manufactured super conducting device than canbe obtained using conventional coils wound in a race trackconfiguration, although that configuration can also be used in this typeof machine. The double-helix design configuration used in the presentinvention is shown in FIG. 2 is described in U.S. Pat. No. 6,921,042B1“Concentric Tilted Double-helix Dipoles and Higher-order MultipoleMagnets,” Goodzeit et al., issued on Jul. 26, 2005.

The objective of this design is to provide a high power density machineespecially suitable for use at low rotor speeds such as for a windturbine generator or a marine propulsion motor. In most applications thefield coil will be stationary and the armature coils will be on a rotor,so that is the implementation that is discussed. However the sameprinciples could apply for a stationary dual section armature with arotating field coil between its 2 sections.

Since the power density is related to the flux linkage between thearmature and field, we can aim for the highest power density from thefollowing considerations:

The Field Coil: The use of a high-field superconducting field coil is anessential requirement for this design in order to provide the highestfield using the smallest mass of conductor. Thus, this design isespecially useful if the highest current density superconductingmaterial can be used in the field coil. An LTS (Low TemperatureSuperconductor) material such as NbTi in a 6-layer double-helix coil caneasily achieve a flux density (field strength) in the aperture of thefield coil of greater than 4 T. However, such conductors operate at˜4.3K and thus would be feasible only if the heat gain from externalsources can be kept low enough. Since the field coil operates at DC, theAC losses in the field coil can be negligibly small.

However, the large torque produced by a low speed, high power machinerequires a substantial cross section of high strength material tosupport the field coil to the frame of the machine to resist thistorque. Thus, the design features a low heat leak, high torque capacitysupport system for the field coil. Using this technique, therefrigeration requirements for the field coil can be reduced to a levellow enough to be supplied by commercially available cryocoolersoperating in that temperature range. Other sources of heat leak into themachine, such as radiation, are mitigated by the use of multilayerinsulation for the field coil cold mass and thermal shields surroundingit.

Armature Coils: Since the design incorporates a field coil essentiallyencapsulated by the rotating armature coils, it is convenient to usethese armature coils as a cryogenic shield for the field coil. Thus, thearmature coils could use either a cryogenically operating normalconducting material, an HTS (High Temperature Superconductor) material,or an LTS (Low Temperature Superconductor) material such as NbTi. Eventhough the armature rotates in a constant field, the direction of thefield seen by the armature conductor reverses during every revolution ofthe armature, thus inducing AC losses in the superconductor as well aseddy current losses in the resistive material used in the armatureconstruction. Thus, the decision on the use of an LTS or HTS materialfor this application would depend on refrigeration requirements for therotor. However, using a resistive material operating at 80K provides avery compact, high density design.

Type of Machine: A “DC type” of machine is especially suitable for useof the dual armature feature. The use of a three-phase winding for therotor armature coils, coupled with a full-wave three-phase rectifier,can easily allow a high DC voltage (i.e. 12,500 VDC) in a compactmachine.

FIG. 3 shows an isometric cross section of the preferred embodiment ofthe machine. A freely rotating dual armature has inner (302) and outer(303) armature sections that are separated by a radial distance thatpermits the placement of the stationary field coil (314) between them.The assembly (described in detail below) has its electrical andcryogenic connections at one end (shown on the right) and its mechanicalconnections at the other end (shown on the left). The entire rotor andfield coil assembly is in a vacuum environment within the outer shellthat is composed of a long section (311) and 2 end sections (310, 312).

The field coil (314) has support and confinement pieces (313) thatentirely encapsulate the coil. A utility tube (not shown) provides thecryogen supply and exhaust for the field coil. It also includes currentleads that make a transition from the superconducting to the normalstate. This utility tube would pass through the outer shell (311) andattach to the field coil enclosure volume (313) at the hole (320). Thefield coil cryogenic mass (313,314) may also be insulated with layers ofmultilayer insulation (not shown) in the space (315) in order to reducethe radiation heat the field coil would receive.

A connecting hub (318) is used to form a structural bridge from thefield coil assembly (313,314) to a high torque, low heat leakcylindrical shaft assembly (317). This shaft assembly connects via asplined connection (319) to the vacuum tank shell (311) of the frame ofthe machine. The frame of the machine is connected to a base plate (notshown) by means of supports (not shown).

The dual armature sections (302, 303) are mounted on a rotor assemblywith an external hub (301) and inner shaft (326). A structural piece(327) attached to the machine frame (311) supports the other end of therotor. Bearings (305, 306) at each end of the rotor allow it to rotatefreely. The inner armature section (302) is supported on the inner shaftportion (326) of the rotor hub and the outer armature section (303) issupported on a cylindrical base (322) that is connected to the externalrotor hub (301) by means of the connecting hub (325).

If their coils are to be cryogenically cooled, the armature sectionswould each have additional support and confinement pieces (316) thatentirely encapsulate them. Utility passages (not shown) in the rotor endhub pieces (301, 325) would allow for connections for the electricalwiring, cryogen supply and exhaust for the rotor coils. The electricaland cryogen lines would go through the hollow interior of the shaft(326). At one end of the rotor, the hub (301) is connected to a hightorque capacity connection such as a splined coupling (304). This end ofthe rotor could be connected to an extension shaft (not shown) thatmates with the splined connection (304). The purpose of such anextension shaft is to provide a high torque capacity, low heat leakshaft for transmitting mechanical power to or from this machine. Such anextension shaft is housed in a vacuum tank closure (not shown) that isassembled to the end flange (312) of the electrical machine.

At the other end of the rotor, the shaft (326) is connected to a lowheat leak utility tube (307) with bearing and seal assemblies (308) thatare mounted in the end closure (310). The utility tube provides accessto the inner region of the rotor shaft (326) to permit the passage ofelectrical leads and cryogenic supply and return for the armature coils.

An assembly of brushes (309) may connect the armature coils to anexternal rectifying circuit (not shown) that converts the AC voltage ofthe coils to DC. Other aspects of this invention include a method ofsupporting the field coil cold mass (313, 314). The loads that need tobe managed include gravity, inertia, and the reaction torque produced onthe field coils. For the case of high power, low speed applications thereaction torque can be many times greater than the gravity and inertialoads on the structure.

Thus, in order to manage the reaction torque, this aspect of theinvention includes a low heat leak, high strength, reaction torqueassembly (317, 319). This assembly consists of a nested set of connectedconcentric cylinders of high strength, low heat leak material that forma long path between the cryogenic environment of the field coil and theambient temperature of the environment. In order to engage the reactiontorque assembly to the frame of the machine (i.e. the vacuum tank), asplined connection (319) is provided so that the reaction torqueassembly can be assembled into the machine and transmit the torque fromthe field coils to the frame with high strength joints. Thisconstruction technology has been described in U.S. Patent applicationNo. 61/041,673 for “Low Heat Leak, High Torque Power Shaft for CryogenicMachines,” submitted Apr. 2, 2008 by Carl L. Goodzeit.

In order to provide an enhanced magnetic field for the machine, theassembly can be provided with an external layer of iron (not shown) thatcan be placed around the periphery of the vacuum tank (311). The ironprovides a lower reluctance return path for the flux which increases thefield intensity of the coils and provides shielding of the straymagnetic field.

The field map shown in FIG. 1 was calculated using double helix geometrycoils that were illustrated in FIG. 2. However, any dipole magnet with avertical field inside its circular aperture would create the same fieldpattern. A common configuration that has been used for superconductingmagnets is the race track configuration, illustrated in FIG. 4.

Racetrack coils are so-called because the superconductor windings (401,402) follow a path similar in shape to a long racetrack oval. The coilturns in the long sections (404) are parallel to the axial direction Z(403) of the cylindrical coil. The two windings (401, 402) of a dipoleracetrack coil create a magnetic field in the Y-direction (405) in thestraight section (404) of the coil.

The superconducting coils will require a cryogenic system and vacuumvessel with seals and bearings plus electrical leads that can transitionbetween ambient and superconducting temperature. All of these componentscan be supplied by currently existing cryogenic technology.

The polarity of the electromagnetic frequency in each coil changes asthe armature rotates in the field. Thus, in a generator the outputvoltage of each coil needs to be rectified in order to produce aunidirectional (or DC) current. In the preferred embodiment of theinvention, this rectification is accomplished by connecting the coilends to slip rings from which the current is transferred by means ofbrushes to a rectifier. Thus, with three armature coils, three sliprings can be used with brushes and a three-phase full-wave bridgerectifier to produce a DC current equal to the summation of the currentin each of the three coils at a voltage that is almost as great as thepeak generated voltage of each coil.

The preferred embodiment configuration of the present invention willalso work as a motor with DC current supplied to the device.Furthermore, without the use of external rectification, the machine canemulate an AC 3-phase generator or a synchronous motor. In theembodiment of this machine using superconducting coils in both thearmature and field coils, “superconducting current leads” that make atransition from the cryogenic environment to the ambient temperatureregion are used. Such leads are commercially available and are known tohave a very low level of thermal loss to the cryogenic region.

The present technology can be used with wind turbines, which arecharacterized by having a very low-speed power source, such as atypically 12-20 rpm propeller drive. The conventional technology forwind turbines requires the use of a gear box to increase the speed ofthe electric generator to be compatible with the generation of power byconventional machines. However, the gear box for high power windturbines is a technically difficult, massive component of considerableexpense. The ability of the invented fully-superconducting machine todevelop a high voltage at low speed using a plurality of multi-turncoils on the rotor and a high-field superconducting field coil enablesthe generation of electric power using a direct device, and thuseliminates the expensive gear box.

The present technology can be used with marine propulsion motors, whichare required to have high power density (i.e. a high power to weightratio), operate at low speed (i.e. typically 120 rpm), and have a veryhigh power output (i.e. 25 MW or higher). The two types ofsuperconducting machines that have been used for marine propulsionapplications are the homopolar machine and the AC synchronous machines.Homopolar motors are sought as a desirable technology for thisapplication, as discussed by Superczynski in the paper that was cited inthe Background section discussion of Prior Art. However, conventionalhomopolar motors have serious drawbacks that include excessively highcurrent supply to achieve even moderate power levels and the inabilityto use a completely superconducting machine (i.e. both superconductingfield coils and superconducting rotor coil).

Existing technology marine prolusion motors are also based on the use ofsynchronous motor technology (AC) machines that use a superconductingrotor (field coil) and a normal conducting stator (armature). Theinvented technology can effectively double the flux linkage between thefield and armature, thus doubling the back emf of the motor at a givenspeed and increasing the power by a factor of four. This amounts toincreasing the power density for a given size motor by a factor of fourand thus provides an important improvement for marine propulsion motors.

The present technology can be used with electric motors, which can beconsidered for aircraft propulsion if they have a high enough power toweight ratio. The disclosed invention has the advantage of the abilityto provide an approximately 4 times higher power to weight ratio thanexisting types of electric propulsion motors. This dual armature motorcould operate at the higher speeds (e.g. 1200 rpm) that would besuitable for a propeller-driven craft.

The present technology can be used with generation of hydroelectricpower. The present invention is especially suitable for low speed, hightorque applications and thus can be driven by a hydraulic turbine.Hydraulic power generation would benefit by the use of this invention toreduce the size and mass, and to increase the power density of thegenerator.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby, and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved, especially as they fall within the breadthand scope of the claims here appended.

1. A motor/generator machine for producing motor forces or generatingelectrical power comprising: a superconducting 2-pole field coil of acylindrical configuration having a first longitudinal axis that isaligned along the center point of the cylindrical field coil, said fieldcoil configured to produce an internal magnetic field that istransversely disposed in a first direction from said longitudinal axisand said magnetic field having a return flux that is external to saidfield coil; an internal armature of a cylindrical configuration having asecond longitudinal axis that is parallel to the first longitudinalaxis, said internal armature being placed within said field coil suchthat there is a radial spacing distance between an exterior surface ofthe internal armature and an internal surface of the field coil, saidinternal armature having at least one 2-pole coil that links with theinternal flux created by the field coil; an external armature of acylindrical configuration having a third longitudinal axis that isparallel to the first longitudinal axis, said external armature beingplaced outside said field coil such that there is a radial spacingdistance between the interior surface of the external armature and theexterior surface of the field coil, said external armature having atleast one 2-pole coil that links with said external return flux createdby the field coil, and said internal and external armatures are coupledtogether so to form a unified armature assembly.
 2. The motor/generatorof claim 1 wherein the armature assembly is rotatable.
 3. Themotor/generator of claim 1 wherein the field coil is rotatable.
 4. Themotor/generator of claim 1 wherein the internal armature is made of asuperconducting material.
 5. The motor/generator of claim 1 wherein thefield coil is made of a high temperature superconducting (HTS) material.6. The motor/generator of claim 1 wherein the external armature is madeof a superconducting material.
 7. The motor/generator of claim 1 whereinat least one of said internal or external armature have a multi-phasearmature of n-phases and a plurality of coils so that the magnetic axisof each coil is azimuthally spaced at 360°/n from a neighboring coil. 8.The motor/generator of claim 1 wherein at least one of said field,internal armature, or external armature coils have four or more poles.9. The motor/generator of claim 1 further comprising: a connectorbetween at least one of said internal or external armatures and a largeshaft for transmitting mechanical power to or from the machine, asupporter assembly for supporting a rotor with bearings; a connectorbetween at least one of said internal or external armatures and a smallshaft, said small shaft provides a mounting for a current transferdevice having collectors and brushes, and said small shaft providingaccess to the interior of the rotor to supply and exhaust coolant for atleast one of said internal or external armature coils.
 10. Themotor/generator of claim 1 wherein at least one of said field orarmature coils are double-helix coils.
 11. The motor/generator of claim1 further comprising: a cryogenic containment vessel that maintains arefrigerant around the superconducting field coils, said superconductingfield coil being supported directly by the containment vessel.
 12. Themotor/generator of claim 11 wherein the armature sections of the rotorare each cooled by a cooling system that may be separate from that ofthe field coil.
 13. The motor/generator of claim 11 further comprising avacuum vessel that houses said field coil, armature sections, andassociated cooling systems, wherein the rotor shaft ends extend out ofthe vacuum environment with a bearing and seal assembly to permitrotation of the rotor and prevent leakage, said vacuum vessel forming aframe of the machine having a mounting surface.
 14. A motor/generatormachine for producing motor forces or generating electrical powercomprising: a superconducting 2-pole field coil of a cylindricalconfiguration having a first longitudinal axis that is aligned along thecenter point of the cylindrical field coil, said field coil configuredto produce an internal magnetic field that is transversely disposed in afirst direction from said longitudinal axis and said magnetic fieldhaving a return flux that is external to said field coil; a internalarmature of a cylindrical configuration having a second longitudinalaxis that is parallel to the first longitudinal axis, said internalarmature being placed within said field coil such that there is a radialspacing distance between an exterior surface of the internal armatureand an internal surface of the field coil, said internal armature havingat least one 2-pole coil that links with the internal flux created bythe field coil; a external armature of a cylindrical configurationhaving a third longitudinal axis that is parallel to the firstlongitudinal axis, said external armature being placed outside saidfield coil such that there is a radial spacing distance between theinterior surface of the external armature and the exterior surface ofthe field coil, said external armature having at least one 2-pole coilthat links with said external return flux created by the field coil, andsaid internal and external armatures are coupled together so to form aunified armature assembly; a connector between at least one of saidinternal or external armatures and a large shaft for transmittingmechanical power to or from the machine; a rotor having a small shaft ona first end and a large shaft on a second end, said armature connectedto the small and large shafts of said rotor; a supporter assembly forsupporting said rotor with bearings; a connector between at least one ofsaid internal or external armatures and said small shaft, said smallshaft provides a mounting for a current transfer device havingcollectors and brushes, and said small shaft providing access to theinterior of the rotor to supply and exhaust coolant for at least one ofsaid internal or external armature coils.
 15. The motor/generator ofclaim 14 wherein said rotor shaft extends out the motor/generator with abearing and seal assembly to permit rotation of the rotor and preventleakage of the refrigerant.
 16. The motor/generator of claim 14 whereinhigh temperature superconducting materials are used for at least one ofthe field or armature coils.
 17. The motor/generator of claim 14 whereinlow temperature superconducting materials are used for at least one ofthe field or armature coils.
 18. The motor/generator of claim 14 whereinnon-superconducting materials are used for at least one of the armaturecoils.
 19. A motor/generator machine for producing motor forces orgenerating electrical power comprising: a superconducting 2-pole fieldcoil of a cylindrical configuration having a first longitudinal axisthat is aligned along the center point of the cylindrical field coil,said field coil configured to produce an internal magnetic field that istransversely disposed in a first direction from said longitudinal axisand said magnetic field having a return flux that is external to saidfield coil; an internal armature of a cylindrical configuration having asecond longitudinal axis that is parallel to the first longitudinalaxis, said internal armature being placed within said field coil suchthat there is a radial spacing distance between an exterior surface ofthe internal armature and an internal surface of the field coil, saidinternal armature having at least one 2-pole coil that links with theinternal flux created by the field coil; an external armature of acylindrical configuration having a third longitudinal axis that isparallel to the first longitudinal axis, said external armature beingplaced outside said field coil such that there is a radial spacingdistance between the interior surface of the external armature and theexterior surface of the field coil, said external armature having atleast one 2-pole coil that links with said external return flux createdby the field coil, and said internal and external armatures are coupledtogether so to form a unified armature assembly; a rotor having a smallshaft on a first end and a large shaft on a second end, said armatureconnected to the small and large shafts of said rotor; a connectorbetween at least one of said internal or external armatures and saidlarge shaft for transmitting mechanical power to or from the machine, asupporter assembly for supporting said rotor with bearings; a connectorbetween at least one of said internal or external armatures and saidsmall shaft, said small shaft provides a mounting for a current transferdevice having collectors and brushes, and said small shaft providingaccess to the interior of the rotor to supply and exhaust coolant for atleast one of said internal or external armature coils.
 20. Themotor/generator of claim 19 wherein the assembly is used as a marinepropulsion motor.
 21. The motor/generator of claim 19 wherein theassembly is used as an aircraft propulsion motor.
 22. Themotor/generator of claim 19 wherein the assembly is used as an electricgenerator driven by wind power.
 23. The motor/generator of claim 19wherein the assembly is used as an electric generator driven by ahydraulic turbine.